The widow of murdered spy Alexander Litvinenko said she does not believe a public inquiry into his death has been sparked by international tension with Russia.

Marina Litvinenko insisted that the probe would have happened anyway without pressures over Ukraine.

She said: "I've been waiting for this decision since February.

"I believed it would happen one day, and it's happened when it's a very difficult situation in the world.

"What happened in Ukraine has made my case a very different prospect, but I'm definitely sure (the decision) was not made because of this."

She said she has not fought for a public inquiry as a move against the UK or Russia, but for the truth. She continued: "I've done this for justice, I've done this for truth.

"I would like to show people you are able to get justice in any difficult situation."

Former KGB bodyguard Andrei Lugovoi and Dmitri Kovtun have been identified as the prime suspects in the killing, but both deny any involvement and remain in Russia.

Mrs Litvinenko says she believes that they will never face extradition to the UK. Referring to Russian president Vladimir Putin, she said: "I believe he will never change his mind."

But she said the public inquiry offered "a different type of justice".

Although Mrs Litvinenko and her lawyers will not be able to see secret material that will be part of the evidence in the inquiry, the chairman can take it into account, unlike in an inquest.

Solicitor Elena Tsirlina said: "The advantage of having a public inquiry is that the material that could not be disclosed as part of the inquest can now be seen by the chair of the inquiry. He will be able to take it into account, although that material will not be publicly disclosed."

Mrs Litvinenko said: "This is a different type of justice. For me it's very important, this type of justice, because there will still be consideration of why 'Sasha' died." The 43-year-old Russian spy died after drinking tea laced with radioactive polonium-210 with two former colleagues at a London hotel in 2006.